Positioning systems and methods for determining the location of a mobile communication device

ABSTRACT

A localization approach based on cable length detection. In one aspect, a method performed by a positioning system for determining the location of a mobile communication device (MCD) is provided. In some embodiments, the method includes the positioning system determining a cable length value representative of the length of the cable connecting a base station to a radio head serving the MCD. The positioning system then determines a location of the MCD based on the determined cable length.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 35 U.S.C. §371 National Phase Entry Applicationfrom PCT/SE2015/051323, filed Dec. 10, 2015, and designating the UnitedStates, which claims priority to U.S. Provisional Application No.62/121,061, filed on Feb. 26, 2015. The contents of both applicationsare incorporated by reference.

TECHNICAL FIELD

This disclosure relates to determining the location of a mobilecommunication device (MCD).

BACKGROUND

A cellular communication system comprises a number of base stations,each of which uses one or more antenna elements to serve one or morecells (geographic regions). The base station functions to communicatewith mobile communication devices (MCDs) (e.g., smartphones, tables,phablets, etc.) to provide the MCD with access to a network (e.g., theInternet or other network). A base station typically includes at leastan antenna element, a radio unit (RU) and a digital unit (DU). An RUtypically includes a receiver and a transmitter in order to transmitdata to and receive data from an MCD.

The signal transmitted by a base station may be received by an MCD withpoor quality when the MCD is in certain locations. For example, when anMCD is located inside of a building (e.g., an office building, a home)and the base station antenna that is serving the MCD is located outsideof the building, the MCD may not receive a strong signal from theantenna. Likewise, in such a situation, in order for the MCD to transmita signal to the base station, the MCD may have transmit the signal usingmore power than the MCD would have had to use had the MCD been locatedoutdoors. Such a situation reduces the MCD's battery life.

A solution to this problem is to install small transceiver units(a.k.a., “radio heads”) indoors and connect each of the radio heads toan RU of a base station using a cable (e.g., local area network (LAN)cable, such as an Ethernet cable). For example, in a large building withpoor network coverage, a radio head connected via a cable to an RU maybe placed on each floor of the building. Such a radio head receives viathe cable a signal transmitted from the RU and then retransmits thesignal wirelessly so that the signal will be received with good qualityby an MCD located in the vicinity of the radio head. Likewise, when theMCD transmits a wireless signal, the signal is picked up by the radiohead in the vicinity of the MCD and retransmitted by the radio head tothe RU via the cable. In this way, a base station can provide goodindoor coverage. Accordingly, radio heads include one or more antennaelements for broadcasting and receiving wireless signals, and radioheads may also include amplifiers so that a received signal (e.g., asignal from an RU or a wireless signal from an MCD) can be amplifiedbefore it is retransmitted.

One such commercial solution is the Ericsson “Radio Dot System” (RDS).In an RDS, multiple (e.g., one to eight) radio heads are each connectedto an RU via an Ethernet cable. The radio heads receive power as well asthe communication signals via the cable. In the downlink, each suchradio head transmits with a maximum power of 100 mW. Power amplifiersare located in the radio head.

Emergency positioning needs (e.g., E-911) and other location services(LCS) require the position of an MCD to be determined within certainhorizontal and vertical accuracies. For example, emergency positionrequirements may require horizontal inaccuracy to be below 50 meters.Additionally, the vertical inaccuracy requirement has recently beentightened to 3 meters in North America in order to better distinguishbetween floors in buildings.

Accordingly, there is a need for an improved system for determining thelocation of an MCD.

SUMMARY

The fulfillment of emergency positioning requirements when an MCD islocated indoors remains a challenging problem. For example, satellitepositioning is not always available indoors. Additionally, cell IDpositioning (i.e., determining the location of the MCD based on the cellID of the cell in which the MCD is located) may not be accurate enoughto meet the stringent emergency positioning needs. Thus, there exists aneed to improve positioning of an MCD, particular when the MCD islocated indoors.

This disclosure relates to systems and methods for determining thelocation of an MCD. In one aspect, a method is performed by apositioning system for determining the location of the MCD. Thepositioning system includes one or more of: a positioning node and abase station.

The method includes the step of determining a cell in which the MCD islocated (e.g., receiving a message including a cell identifier (cell ID)identifying the cell in which the MCD is located). The determined cellis served by a serving base station connected to a set of radio heads.Each one of the radio heads included in the set of radio heads isconnected to the base station via a cable. One of the radio headsincluded in the set is serving the MCD.

The method further includes determining a cable length value (e.g., acable loss value) representative of the length of the cable connectingthe base station to the radio head serving the MCD.

The method further includes determining the location of the MCD based onthe determined cable length value. The step of determining the locationof the MCD based on the determined cable length value comprises usingthe determined cable length value to obtain location information for theMCD, the location information being associated with a fingerprint andcomprising at least: i) a set of polygon coordinate vectors or ii) a setof coordinates derived from the set of polygon coordinate vectors.

In some embodiments, using the determined cable length value to obtainthe location information for the MCD includes: i) forming a fingerprintusing the determined cable length value (the fingerprint beingassociated with at least one of: the set of polygon coordinate vectorsand the set of coordinates derived from the set of polygon coordinatevectors); and ii) using the fingerprint to obtain the locationinformation for the MCD. In some embodiments, the fingerprint isassociated with the set of polygon coordinate vectors, and the set ofpolygon coordinate vectors define a polygon and comprise at least threepolygon coordinate vectors, each polygon coordinate vector comprising atleast a first coordinate (e.g., longitude) and a second coordinate(e.g., latitude).

In some embodiments, the method further includes obtaining one or moremeasured radio property values, wherein forming the fingerprint usingthe determined cable length value comprises forming the fingerprintusing both the determined cable length value and the one or moremeasured radio property values. In some embodiments, the one or moremeasured radio property values comprises one or more of: a pathlossvalue, a cell identifier, a received signal strength (RSS) value, atiming advance (TA) value, and angle of arrival (AoA) values.

In some embodiments, using the fingerprint to obtain the locationinformation comprises sending to a database server a query for locationinformation, the query comprising the fingerprint, wherein the databaseserver uses the fingerprint to lookup the location information in thedatabase.

In some embodiments, the location information comprises the set ofcoordinates derived from the set of polygon coordinate vectors, and theset of coordinates derived from the set of polygon coordinate vectorscorresponds to the center of gravity of a polygon defined by the set ofpolygon coordinate vectors.

In another aspect, a method for constructing a database for storinglocation information for use in determining the location of a user isdescribed. The method includes determining the location of a mobilecommunication device (MCD), said location being defined by a set of twoor more coordinates (e.g., latitude, longitude, altitude). Thedetermined location may be a high precision location. The method furtherincludes generating a first fingerprint using a cable length valuerepresenting the length of a cable connecting a radio head to a basestation, wherein at the time the location of the MCD was determined theradio head was serving the MCD. The method further includes associatingthe first fingerprint with the determined location. The method furtherincludes determining a set of locations wherein each location in the setis associated with a fingerprint matching the first fingerprint. Themethod further includes forming a polygon based on the determined set oflocations, the polygon being defined by a set of three or more polygoncoordinate vectors, each said polygon coordinate vector identifying adifferent vertex of the polygon. The method further includes associatingthe first fingerprint with at least the set of polygon coordinatevectors or a set of coordinates derived from the set of polygoncoordinate vectors.

In some embodiments, the method further includes obtaining a measuredradio property value, wherein generating the fingerprint using thedetermined cable length value comprises generating the fingerprint usingboth the determined cable length value and the measured radio propertyvalue.

In another aspect, a positioning system for determining the location ofa mobile communication device (MCD) is provided. In some embodiments,the positioning system comprises one or more of: a positioning node; anda base station connected to a set of radio heads, wherein each one ofthe radio heads included in the set of radio heads is connected to thebase station via a cable. The positioning system is configured toperform the methods described herein.

The above and other aspects and embodiments are described below.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram of a positioning system, according to someembodiments.

FIG. 2 is a flow chart of a location process, according to someembodiments.

FIG. 3 is a flow chart of a process for determining a cable lengthvalue, according to some embodiments.

FIG. 4 is a flow chart of a process for determining a cable lengthvalue, according to some embodiments.

FIG. 5 is a flow chart of a process for determining the uplink path lossbetween an MCD and the serving radio head, according to someembodiments.

FIG. 6 is a flow chart of a process for using a determined cable lengthvalue to obtain location information for an MCD, according to someembodiments.

FIG. 7 is a flow chart of a location process, according to someembodiments.

FIG. 8 is a flow chart for creating a database that associatesfingerprints with location information, according to some embodiments.

FIG. 9 is a block diagram of a positioning node apparatus, according tosome embodiments.

FIG. 10 is a block diagram of a digital unit apparatus, according tosome embodiments.

DETAILED DESCRIPTION

Disclosed herein are systems and methods for determining the location ofan MCD that is being served by a radio head by determining a valuecorresponding to the length of the cable connecting the serving radiohead to a base station (e.g., by determining the cable gain/loss). Asignificant advantage of the disclosed systems and methods is that theymay provide up to eight times reduced position inaccuracy as compared tocell ID positioning. Additionally, the disclosed techniques can be usedto improve the accuracy of Radio Measurements Trace processing servers(TPSs). TPSs play a major role in modern radio access networkoptimization by using geolocation measurements from MCDs to identifyproblems in the network. By using the positioning techniques disclosedherein, the position of specific events may be determined with higheraccuracy, thereby improving TPS performance.

FIG. 1 is a block diagram of a positioning system 100, according to someembodiments. The positioning system 100 includes a base station 104,which comprises a radio unit (RU) 103 and a digital unit (DU) 105. TheRU 103 and the DU 105 may be housed in the same housing or they behoused in separate housings that may or may not be co-located. In someembodiments, such as where the RU 103 and the DU 105 are not coupled inthe same housing, DU 103 may be connected to the RU 103 via a cable(e.g., optical, electrical). A set of one or more radio heads 107 (e.g.,radio heads 107 a to 107 n in the example shown) is connected to basestation 104 (more specifically, the radio heads are connected to RU 103of base station 104). In some embodiments, each radio head 107 isconnected via a cable 108, such as a local area network (LAN) cable(e.g., an Ethernet cable or other LAN cable), to the RU 103. Radio heads107 includes one or more antenna elements for wirelessly transmittingsignal to an MCD 120 and for wirelessly receiving signal transmitted byMCD 120. In some embodiments, radio heads 107 may further comprise apower amplifier. In some embodiments, RU 103 may comprise an indoorradio unit (IRU), and radio heads 107 may deliver mobile broadbandaccess to the MCD 120 in a broad range of indoor locations.

Base station 104 may be connected to a core network 130 that includes apositioning node 140 for processing position requests as well as othercore network nodes (e.g., a Mobility Management Entity (MME), a ServingGateway (SGW), and Packet Data Network Gateway (PGW)). However, theembodiments disclosed herein are not limited to any specific type ofcore network. In embodiments where core network 130 is a core network ofa Long Term Evolution (LTE) system, the positioning node 140 maycomprise or consist of an Evolved Serving Mobile Location Center(E-SMLC) and the base station 104 may comprise or consist of an enhancedNode B (eNB). In embodiments where core network 130 is a WCDMA 3Gcellular system, the positioning node 140 may comprise or consist of astand-alone Serving Mobile Location Center (SAS) and the base station104 may comprise or consist of a radio network controller (RNC).

In some embodiments, an LCS client 160 may transmit a positioningrequest to positioning node 140. In some embodiments, as shown in FIG.1, LCS Client 160 may be a computer server connected to a network (e.g.,the Internet), and thus is external to the core network 130.

In embodiments where core network 130 is an LTE network, a GatewayMobile Location Center (GMLC) in network 130 may receive from theexternal LCS client 160 a position request for a particular locationservices target, e.g., MCD 120. The GMLC may then transmit the positionrequest to an MME in core network 130. The MME may in turn forward therequest to the positioning node 140 (E-SMLC in this example). Thepositioning node 140 may then process the location services request toperform a positioning of the target MCD 120. In some embodiments, thepositioning node 140 may perform some or all of the processing forperforming the calculations described in connection with FIGS. 2-6. Inother embodiments, the base station 104 may perform some or all of theprocessing for performing the calculations described below in connectionwith FIGS. 2-6. The positioning node may then return the result of theposition request back to the MME, which in turn will forward theposition result back to requesting LCS client 160 (e.g., through theGMLC and network 110).

As described below, in situations where MCD 120 is being served by aradio head 107, such as radio head 107 a (i.e., MCD 120 is in thevicinity of radio head 107 a and is receiving and processing the signalstransmitted by radio head 107 a, and vice-versa), positioning node 140is configured to determine the location of the MCD 120 by determining avalue representative of the length of the cable connecting the radiohead 107 that is serving MCD 120 to base station 104.

In the downlink direction, data from the DU 105 is sent to the RU 120where it is transmitted in analogue form to the radio heads 107. In theuplink direction, the signal received on each of the radio heads 107from the MCD 120 is amplified and then sent to the base station 104. Insome embodiments, the gain of the amplifier can be set individually foreach radio head 107. In some embodiments, there may be significantlosses (e.g., up to 30 dB) associated with each cable (up to 200 m)connecting the one or more radio heads 107 to the base station 104. Insome embodiments, such loss values may be configured in a database inbase station 104.

In some embodiments, an estimate of the cable loss (L_cable) of thecable 108 connecting base station 104 with the radio head 107 servingthe MCD 120 is calculated and then used to determine the location of MCD120. The estimated cable loss can be used to determine a position of theMCD because, in many networks, each cable 108 connecting one of theradio heads 107 to base station 104 has a unique cable loss (cable lossis directly proportional to cable length and in many networks each radiohead connected to a particular RU of base station 104 is connected bycable having a length that is different than the lengths of the othercables used to connect the other radio heads to the RU). Thus, if theestimated cable loss value is accurate enough, it can be mapped to aspecific location because the actual cable lengths (or cable losses) maybe measured at installation of the radio heads. Thus, the location ofthe MCD can be determined more accurately as the cell coverage area maybe split up into smaller areas corresponding to each radio head.Furthermore, in embodiments where each radio head is associated with onefloor of a building, it may be further possible to resolve locationinformation to a floor of that building.

Additionally, in some embodiments a fingerprint can be formed using,among other things, a cable length value (e.g., the cable loss value)determined as described herein. This fingerprint can be associated withlocation information (e.g., a set of polygon coordinate vectors thatdefine an adaptive enhanced cell ID (AECID) polygon and/or a set ofcoordinates derived from the set of polygon coordinate vectors (e.g.,the derived set of coordinates corresponding to the center of gravity ofthe polygon)). As used herein a “fingerprint” is a set of one or moremeasured/determined values or a set of one or more values derived fromthe measured values.

For example, in some embodiments a fingerprint is formed from adetermined cable length value and a set of one or more measured radioproperty values, which may include one or more of: a pathloss value, acell identifier (ID), a received signal strength (RSS) value, a timingadvance (TA) value, and angle of arrival (AoA) values. The advantage ofassociating a fingerprint with location information (e.g., a set of oneor more coordinate vectors) is that, after the association has beencreated, a positioning system can obtain fingerprint information (e.g.,determined cable length value, RSS, pathloss, TA, AoA, etc.) from, forexample, an MCD and/or a base station serving the MCD, and use theobtained fingerprint information to generate a fingerprint and then usethe fingerprint to query a location information database for locationinformation (e.g. coordinate vector(s)) associated with the generatedfingerprint.

Referring now to FIG. 2, FIG. 2 is a flow chart of a positioning process200, according to some embodiments, performed by a positioning systemfor determining the location of MCD 120. In some embodiments, thepositioning system comprises one or more of: MCD 102, positioning node140, and base station 104.

Referring to FIG. 2, step 202 includes determining a cell in which MCD120 is located, the determined cell being served by a serving basestation (base station 104, in this example). As discussed above,cellular systems may be divided into cells (which may overlap), and eachcell may be served by one specific base station. In some embodiments,step 202 comprises or consists of the positioning system obtaining acell identifier (Cell ID) identifying the cell in which the MCD islocated (e.g., receiving a message comprising the Cell ID).

In some embodiments, after step 202, the positioning system determineswhether the determined cell is being served by a plurality of radioheads (step 203). If this is the case, then the process proceeds to step204. For example, in step 203 the positioning system may use the Cell IDto obtain a database record from a database, which database recordincludes information identifying whether or not the determined cell isbeing served by a plurality of radio heads.

Step 204 includes determining a cable length value (C_length)representative of the length of the cable connecting the serving basestation to the radio head serving the MCD. In some embodiments,determining the cable length value consists of determining a cable lossvalue denoted L_cable. In some embodiments, the positioning node 140 mayinstruct the base station 104 to perform step 204.

In step 206, the determined cable length value is used to obtainlocation information for the MCD. For example, the determined cablelength value can be a fingerprint (or can be used to form a fingerprintas described below with reference to FIG. 6) that is used in an AECIDfingerprint positioning method. Accordingly, the location informationobtained in step 206 may define an area in which the MCD is likely to befound. In some embodiments, the location information obtained in step206 is a set of polygon coordinate vectors that together define apolygon defining an area in which the MCD is likely to be found. Thepolygon defined by the polygon coordinate vectors may be an AECIDpolygon, such as a polygon formed by the method disclosed in U.S. PatentPub. No. 2013/0210458 or by the method disclosed in reference [1].

In some embodiments, each polygon coordinate vector has only twocoordinates that define a point (e.g., a vertex of the polygon) on a twodimensional surface (a latitude and longitude). In other embodiments,each polygon coordinate vector has at least three coordinates thatdefine a point in a three dimensional space (e.g., latitude, longitude,and altitude). In some embodiments, the location information obtained instep 206 is a set of coordinates derived from a set of polygoncoordinate vectors (e.g., the derived set of coordinates correspondingto the center of gravity of the polygon defined by the polygoncoordinate vectors).

In some embodiments, obtaining the location information for the MCDcomprises: obtaining a set of predetermined cable length values;determining which one of a set of predetermined cable length values isclosest to the determined cable length value; and estimating thelocation of the MCD using the predetermined cable length value that wasdetermined to be closest to the determined cable length value.

In some embodiments, estimating the location of the MCD using thepredetermined cable length value that was determined to be closest tothe determined cable length value comprises using the predeterminedcable length value to retrieve location information from a database(e.g., from a table). That is, each of the predetermined cable lengthvalues may be stored in a table that maps the predetermined cable lengthvalue to a position (e.g., to a floor of a building or a set ofcoordinates). Thus, determining an estimate of the cable length valueallows one to map that information to a specific area (i.e., the entirearea served by the serving radio head). In some embodiments, estimatingthe location of the MCD further comprises obtaining a path loss valuerepresentative of a path loss between the MCD and the serving radio headand using the path loss value to estimate the distance between the MCDand the serving radio head. This enables path loss feature enables thepositioning system to further narrow the area in which the MCD is likelyto be found. Additionally, in some embodiments, as described herein anAdaptive Enhanced Cell Identity (AECID) fingerprinting method known inthe art could be augmented to take into account location informationdetermined in step 206.

In some other embodiments, determining the location of the MCD based onthe determined cable length value (C_length) comprises: obtaining a setof predetermined cable length values (C_length_pre_i, i=1, 2, . . . ,N); determining a subset of the set of predetermined cable length valuesthat are within a certain threshold distance (T) of the determined cablelength value; and estimating the location of the MCD using thedetermined subset of predetermined cable length values. That is, if|C_length_pre_i−C_length|<T, then C_length_pre_i is included in thesubset of predetermined cable length values that are used to determinethe location of the MCD. In some embodiments, when the subset includestwo or more predetermined cable length values, the location of the MCDmay be determined to be the union of the coverage areas of the radioheads corresponding to the subset of predetermined cable length values.

In some embodiments, step 204 includes calculating a plurality of cablelength values (C_length_i, i=1, 2, . . . , M) (e.g., one cable lengthvalue is calculated for each radio head included in the set of radioheads). This could be needed since different radio heads may havedifferent gain settings depending on the cable length. In thisembodiment, each of the plurality of predetermined cable length values(i.e., C_length_pre_i) is compared against at least one of thecalculated cable length values (C_length_i) in order to determine thepredetermined cable length value that is closest to a calculated cablelength value. For the case where M=N, one computes:

Argmin [|C_length_i−C_length_pre_i|, i] to determine the predeterminedcable length value that is closest to a calculated cable length value.Alternatively, each of the plurality of predetermined cable lengthvalues is compared against at least one of the calculated cable lengthvalues in order to determine the subset of zero or more predeterminedcable length values that are within a threshold distance of a calculatedcable length value. As discussed above, this determined subset ofpredetermined cable length values is used to determine the position ofthe MCD.

In some embodiments, the set of predetermined cable length values may beobtained by retrieving the set of values from a database using the cellID of the cell in which the MCD is located. That is, in someembodiments, the database links each cell ID included in a certain setof cell IDs with a set of cable length values. For example, suppose agiven cell ID (e.g., cell-id-123) identifies a cell served by an RU of abase station that is connected to a set of radio heads. The database maylink the given cell ID with a set of cable length values, where each oneof the cable length values represents the length of the cable connectingone of the radio heads to the RU. The database may be hosted by DU 105,positioning node 140, or another entity.

In some embodiments, a 90% confidence radius (or other pre-configuredconfidence limit) may be calculated for every radio head position bycalculating the standard deviation of C_length_pre_i around determinedC_length. The confidence radius around the radio head will be given asfunction of Standard deviation of C_length_pre_i shown below in theequation below:RH_Conf_Radius=f(Standard_deviation(C_length_pre_i)).

The calculated confidence interval could then be forwarded to a locationbased service or TPS system in a similar manner as Cell ID, TA, andother methods.

FIG. 3 is a flow chart of a process 300, according to some embodiments,performed by the positioning system for determining a cable length value(step 204). As noted above, the positioning system includes one or moreof: positioning node 140 and base station 104.

In step 302, an uplink path loss value (L_ul) representative of theuplink path loss between the MCD and the serving radio head isdetermined. In some embodiments, L_ul may be determined from acalculated downlink path loss (L_dl) value. Thus, in some embodiments,in order to determine L_ul, the positioning node 140 may first order thebase station 104 to determine the downlink path loss (L_dl).Determination of the L_ul value from the L_dl value is described infurther detail below in connection with FIG. 5.

In step 304, a power measurement report comprising an uplink transmitpower value (P_ul_mcd) indicating the transmit power of an uplink signaltransmitted by the MCD is received. In some embodiments, the MCD 120 mayreport its uplink transmit power P_ul_mod. In some embodiments,measurement orders may be transmitted to the MCD 120 from the servingbase station 104 for the MCD to report the P_ul_mcd value. In the caseof a Trace Processing Server (TPS) geolocation scenario, TPS may utilize3G/4G Radio Enhanced Statistics (RES) features which turn onmeasurements on all MCDs to report P_ul_mcd, the uplink transmit power,in measurement reports. These measurements are called UeTxPowermeasurement, and are reported periodically (e.g., as frequently as every2 seconds). Thus, the base station 104 may receive the P_ul_mcd valuefrom the base station and perform further processing using that value.In other embodiments, the base station 104 may forward the P_us_mcdvalue to the positioning node 140 for further processing.

In step 306, an amplifier gain value is obtained. The amplifier gainvalue (G_amp) may be set individually for each radio head 107 a to 107 nor each radio head may use the same amplifier gain value. In the lattercase, only a single cable length value needs to be calculated,otherwise, in the former case the set of cable length values(C_length_i) is calculated, as described above. In some embodiments, thepositioning node 140 and/or base station 104 may obtain G_amp frompreconfigured information stored in a database.

In step 308, the power value representative of the power of the uplinksignal transmitted by the MCD as measured by the serving base station(P_ul_mcd_du) is obtained. In some embodiments, the P_ul_mcd_du valuecan be determined from power headroom reports and the configured maximumvalue of the MCD 120 power. In some embodiments, the received MCD power(P_ul_mcd_du) is measured directly in the DU 105 of base station 104,e.g., after de-spreading in a WCDMA network. In some embodiments, thebase station 104 sends the P_ul_mcd_du value to the positioning node140, for further processing.

In step 310, P_ul_mcd−L_ul+G_amp−P_ul_mcd_du is calculated. In someembodiments, the positioning node 140 performs the calculation in step310. In other embodiments, the base station 104 performs the calculationin step 310. In some embodiments, the cable loss value for the radiohead (L_cable_i) connected to the MCD 120 is calculated according to theequation below:L_cable_i=P_ul_mcd−L_ul+G_amp−P_ul_mcd_du

As described above, the cable loss value L_cable_i is representative ofthe length of the cable connecting the serving base station 104 to theradio head 107 serving the MCD 120.

FIG. 4 is a flow chart of a process 400 for determining a cable lengthvalue, according to other embodiments. In some embodiments, the steps ofcable length value determination process 400 may be performed by apositioning node 140. In other embodiments, the steps of cable lengthvalue determination process 400 may be performed by both a positioningnode 140 and a base station 104. Like, process 300, process 400 includessteps 302-306 (see FIG. 3).

In step 402, the following values are obtained: i) a signal to noise andinterference ratio of the MCD as measured by a DU of the base stationserving the MCD (SINR_mcd_du), ii) an inter-cell interference value(I_du), iii) a thermal noise power value (N0), and iv) a noise factor ofa radio unit of the serving base station (NF_ru).

The SINR_mcd_du value is measured by the DU 105 of the serving basestation 104. Thus, in some embodiments, the base station 104 may obtainthe SINR_mcd_du value and perform further processing using that value.In some embodiments, the DU 105 of base station 104 may simply transmitthe SINR_mcd_du value to the positioning node 140 for furtherprocessing.

The N0+NF_ru value may be estimated in the RU 103 of base station 104.Alternatively, in some embodiments, instead of estimating values ofN0+NF_ru, pre-configured values may be used. In other embodiments,different algorithms may be used to estimate the N0+NF_ru value.

One algorithm for estimating the N0+NF_ru value is the sliding windownoise floor estimation. Since it may not be possible to obtain exactestimates of this value due to neighbor cell interference, theestimation algorithm applies an approximation using the soft minimumcomputed over a long window of time. Thus, this estimation relies on thefact that the noise floor may be constant over very long periods oftime, disregarding the small temperature drift. However, the slidingwindow algorithm has a disadvantage of requiring a large amount ofstorage memory. The amount of storage memory may be particularlytroublesome in cases where a large number of instances of the algorithmare needed, which may be the case when interference cancellation isintroduced in the uplink.

Another algorithm for estimating the N0+NF_ru value is the recursivenoise floor estimation. For example, to reduce the memory consumption ofthe sliding window algorithm described above, one such recursivealgorithm is disclosed in T. Wigren, “Recursive noise floor estimationin WCDMA,” IEEE Trans. Vehicular Tech., vol. 69, no. 5, pp. 2615-2620,2010. The recursive algorithm may reduce the memory requirements of thesliding window algorithm described above by at least a factor of 100.

Thus, the N0+NF_ru value may be estimated by the base station 104 and beused for further processing. In some embodiments, the base station 104may forward the N0+NF_ru value to the positioning node 140 for furtherprocessing.

Once the N0+NF_ru value is obtained, the neighbor cell interferencevalue (I_du) may be determined using the equation shown below.I_du=P_mcd_total−P_ul_mcd_du−N0−NF_ru

A more detailed explanation of the calculation of I_du is disclosed inT. Wigren, “Soft uplink load estimation in WCDMA,” IEEE Trans. VehicularTech., vol. 58, no. 2, pp. 760-772, February 2009, which is incorporatedherein by reference.

In step 404, the following value is calculated, which is representativeof the cable loss value of the cable (L_cable_i) connecting the servingbase station 104 to the radio head 107 serving the MCD 120:L_cable_i=P_ul_mcd−L_ul+G_amp−(SINR_mcd_du+I_du+N0+NF_ru)

Thus, in alternative embodiments, a value representative of(SINR_mcd_du+I_du+N0+NF_ru) may be used in lieu of the P_ul_mcd_du valuedescribed above in connection with step 308 of FIG. 3. The relationshipbetween these two values is shown below:P_ul_mcd_du=SINR_mcd_du+I_du+N0+NF_ru

FIG. 5 is a flow chart of a process 500, according to some embodiments,for determining an uplink path loss value (L_ul) representative of theuplink path loss between the MCD and the serving radio head.

In step 502, a power measurement report comprising a received powervalue (P_dl_mcd) indicating a received power of a downlink signaltransmitted by the serving radio head as measured by the MCD isreceived. In some embodiments, the MCD 120 may measure the receivedpower (P_dl_mcd) for the radio head 107 to which it is connected. Insome embodiments, measurement orders may be transmitted to the MCD 120from the serving base station 104 for MCD to measure the P_dl_mcd value.In the case of a TPS geolocation scenario, TPS may utilize 3G/4G RESfeatures which turn on measurements on all MCDs to report P_(dl mcd),the downlink transmit power, in measurement reports. These measurementsare called UeRxPower measurement and are reported periodically (e.g., asfrequently as every 2 seconds). Thus, the MCD 120 may transmit themeasured P_dl_mcd value in a measurement report as the UeRxPower to thebase station 104. In some embodiments, base station 104 may send theP_dl_mcd value to the positioning node 140 for determination of L_ul,and in other embodiments, determination of L_ul may be performed by thebase station 104.

In step 504, a downlink path loss value (L_dl) is determined, whereinthe determination comprises calculating (P_dl_mcd−Prh), wherein Prh is avalue representative of the power at which the radio head transmittedthe downlink signal. In some embodiments, the configured downlinktransmit power Prh may be known for each radio head 107. Thus, adownlink path loss value (L_dl) may be determined according to theequation below:L_dl=P_rh−P_dl_mcd

In embodiments where all radio heads have a different power (Prh_i) inthe downlink signal, the L_dl_i value may be determined according to theequation below:L_dl_i=Prh_i−P_dl_mcd

Alternatively, in some embodiments, a dedicated measurement may be usedfor L_dl.

In step 506, the uplink path loss value is calculated using thedetermined downlink path loss value. Thus, in some embodiments theuplink path loss value (L_ul) may be determined from the downlink pathloss (L_dl) value determined in step 504. In some embodiments, once theL_dl value is determined, the positioning node 140 may then order thebase station 104 to perform a measurement of the uplink path loss(L_ul). Alternatively, the positioning node 140 may perform ameasurement of the uplink path loss. In some embodiments, it may beassumed (for simplicity) that the propagation conditions of the uplinkare similar to those of the downlink, and thus L_ul=L_dl. For example,in the case of time division duplex, the reciprocity of the propagationcan be used to motivate why L_ul=L_dl.

Alternatively, in the case of frequency division duplex, a calculationthat is correct on average may be made to conclude a functionaldependence between L_ul and L_dl. In such scenarios, a compensationvalue depending on the carrier frequency (f_(carrier)) is typicallyneeded. Thus, the following general relation shown in the equation belowmay be assumed to hold:L_ul=F(L_dl,f_carrier)

The above relation may have errors; however, these errors may be assumedto be small as compared to the cable loss variation that may approach 30dB for the Ethernet cable technology used with certain small cellsystems, such as DTS.

FIG. 6 is a flow chart of a process 600 for performing step 206 (i.e., aprocess for using a determined cable length value to obtain locationinformation for an MCD), according to some embodiments. Process 600begins in step 602, where one or more measured radio property values isobtained. The radio property values obtained in step 602 may include oneor more of: a pathloss value indicating a pathloss between MCD 120 andbase station 104, a cell identifier (ID) identifying base station 104, areceived signal strength (RSS) value indicating the strength of a signalreceived by MCD 120, a timing advance (TA) value, and angle of arrival(AoA) values.

In step 604 a fingerprint is formed using the determined cable lengthvalue (e.g. cable loss value, as described herein) and the obtainedradio property value(s). Forming the fingerprint, in some embodiments,consists of forming a data structure that stores the determined cablelength value and the obtained radio property value(s). In otherembodiments, forming the fingerprint consists of calculating a value orvalues based on the determined cable length value and the obtained radioproperty value(s). For example, a hash function can be used to generatethe fingerprint from the determined cable length value and the obtainedradio property value(s).

In step 606, the fingerprint formed in step 604 is used to retrieve thelocation information. For example, in step 606, positioning node 140 mayform a query comprising the fingerprint and send the query to a databaseserver (DS) 141 that uses the fingerprint to lookup in a locationfingerprint database 142 location information that is associated withthe fingerprint and then provide the retrieved location information topositioning node 140. In some embodiments, the database server 141and/or database 142 may be a component of positioning node 140.

FIG. 7 is a flow chart of a location process 700, according to someembodiments, for locating MCD 120. Process 700 may be performed bypositioning system 100 (e.g., it may be performed, at least in part, bythe positioning node 140 and/or the base station 104).

In step 702, a request is received to locate MCD 120. For example, insome embodiments, the location request may be submitted by a LCS client160 to the positioning node 140, potentially through one or moreintermediaries as described above. In some embodiments, once thepositioning node 140 receives the location request.

In step 704, a cell ID positioning is performed. For example, thepositioning system obtains a cell ID identifying the cell in which MCD120 is located.

In step 705, based on the obtained cell ID, a determination is made asto whether the cell identified by the cell ID is served by a pluralityof radio heads connected to a base station. If yes, the processcontinues to step 706, otherwise the process ends.

In step 706, a cable loss estimate (L_cable) is obtained. The cable lossestimate L_cable value may be obtained by the positioning node 140and/or the base station 104 as described above in connection with FIGS.3-4.

In step 708, a set of one or more radio property values are obtained(e.g., step 708 may be the same as step 602 of process 600).

In step 710, a fingerprint is formed using L_cable and the valuesobtained in step 708 (e.g., step 710 may be the same as step 604 ofprocess 600).

In step 712, a query for location information is submitted to databaseserver 141, where the query includes the fingerprint.

In step 714, location information associated with the fingerprint isreceived from the database server 141. As described above, the locationinformation may comprise a set of polygon coordinate vectors and/or aset of coordinate derived from the coordinate vectors.

In step 716, the location information (or location information derivedtherefrom) is transmitted to the entity that requested the positioningof MCD 120.

FIG. 8 is a flow chart illustrating a process 800 for populatinglocation fingerprint database 142 with location information. Process 800may begin in step 802, where the location of MCD 120 is determined. Thelocation determined in step 802 may be high precision location that isdetermined using, for example, Assisted Global Positioning System(A-GPS) positioning.

In step 804, a first fingerprint is generated using a cable length valuerepresenting the length of a cable connecting a radio head to a basestation, wherein at the time the location of MCD 120 was determined instep 802 the radio head was serving MCD 120.

In step 806, the first fingerprint is associated with the locationdetermined in step 802.

In step 808, a set of locations is determined wherein each location inthe set is associated with a fingerprint matching the first fingerprint.For example, in step 808 a database is searched using the firstfingerprint to find all other locations that are also associated withthe first fingerprint.

In step 810, a polygon is formed based on the determined set oflocations. The polygon being defined by a set of three or more polygoncoordinate vectors, each said polygon coordinate vector identifying adifferent vertex of the polygon.

In step 812, the first fingerprint is associated with locationinformation that comprises at least the set of polygon coordinatevectors or a set of coordinates derived from the set of polygoncoordinate vectors. For example, in step 812 a record is added tolocation fingerprint database 142, which record includes a first fieldfor storing the first fingerprint and a second field for storing thelocation information. In this way, for example, fingerprints can beassociated with location information.

FIG. 9 is a block diagram of a positioning node apparatus, such aspositioning node 140. As shown in FIG. 9, positioning node 140 mayinclude or consist of: a computer system (CS) 902, which may include oneor more processors 955 (e.g., a microprocessor) and/or one or morecircuits, such as an application specific integrated circuit (ASIC),field-programmable gate arrays (FPGAs), a logic circuit, and the like; anetwork interface 905 for connecting apparatus 104 to a network 110; anda data storage system 908, which may include one or more non-volatilestorage devices and/or one or more volatile storage devices (e.g.,random access memory (RAM)). In embodiments where apparatus 140 includesa processor 955, a computer program product (CPP) 933 may be provided.CPP 933 includes or is a computer readable medium (CRM) 942 storing acomputer program (CP) 943 comprising computer readable instructions(CRI) 944 for performing steps described herein (e.g., one or more ofthe steps shown in FIGS. 2-8). CP 943 may include an operating system(OS) and/or application programs. CRM 942 may include a non-transitorycomputer readable medium, such as, but not limited, to magnetic media(e.g., a hard disk), optical media (e.g., a DVD), solid state devices(e.g., random access memory (RAM), flash memory), and the like.

In some embodiments, the CRI 944 of computer program 943 is configuredsuch that when executed by computer system 902, the CRI causes theapparatus 940 to perform steps described above (e.g., steps describedabove and below with reference to the flow charts shown in thedrawings). In other embodiments, positioning node apparatus 140 may beconfigured to perform steps described herein without the need for acomputer program. That is, for example, computer system 902 may consistmerely of one or more ASICs. Hence, the features of the embodimentsdescribed herein may be implemented in hardware and/or software.

FIG. 10 is a block diagram of DU 105, according to some embodiments. Asshown in FIG. 4, DU apparatus 105 may include or consist of: a computersystem (CS) 1002, which may include one or more processors 1055 (e.g., amicroprocessor) and/or one or more circuits, such as an applicationspecific integrated circuit (ASIC), field-programmable gate arrays(FPGAs), a logic circuit, and the like; a network interface 1005 forconnecting DU 105 to network 130; one or more RU interfaces 1008 forconnecting DU 105 to one more RUs; and a data storage system 1012, whichmay include one or more non-volatile storage devices and/or one or morevolatile storage devices (e.g., random access memory (RAM)). In someembodiments, network interface 1005 and RU interface 1008 include atransceiver for transmitting data and receiving data.

In embodiments where DU apparatus 105 includes a processor 1055, acomputer program product (CPP) 1033 may be provided. CPP 1033 includesor is a computer readable medium (CRM) 1042 storing a computer program(CP) 1043 comprising computer readable instructions (CRI) 1044 forperforming steps described herein (e.g., one or more of the steps shownin FIGS. 2-8). CP 1043 may include an operating system (OS) and/orapplication programs. CRM 1042 may include a non-transitory computerreadable medium, such as, but not limited, to magnetic media (e.g., ahard disk), optical media (e.g., a DVD), solid state devices (e.g.,random access memory (RAM), flash memory), and the like.

In some embodiments, the CRI 1044 of computer program 1043 is configuredsuch that when executed by computer system 1002, the CRI causes theapparatus 105 to perform steps described above (e.g., steps describedabove and below with reference to the flow charts shown in thedrawings). In other embodiments, apparatus 105 may be configured toperform steps described herein without the need for a computer program.That is, for example, computer system 1002 may consist merely of one ormore ASICs. Hence, the features of the embodiments described herein maybe implemented in hardware and/or software.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. Thus, the breadth and scope of the present invention shouldnot be limited by any of the above-described exemplary embodiments.Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

Additionally, while the processes described above and illustrated in thedrawings are shown as a sequence of steps, this was done solely for thesake of illustration. Accordingly, it is contemplated that some stepsmay be added, some steps may be omitted, the order of the steps may bere-arranged, and some steps may be performed in parallel.

REFERENCES

-   [1] T. Wigren, Adaptive Enhanced Cell-ID Fingerprinting Localization    by Clustering of Precise Position Measurements, IEEE TRANSACTIONS ON    VEHICULAR TECHNOLOGY, VOL. 56, NO. 5, September 2007.

ABBREVIATIONS

-   -   RH_i=Radio head i of a maximum of n.    -   P_ul_mcd=The uplink transmit power as measured by the MCD [dBw].    -   P_dl_mcd=The measured received power in the downlink as measured        by the MCD [dBw]    -   L_ul=The uplink path loss between the MCD and the serving radio        head [dB].    -   L_dl=The downlink path loss between the serving radio head and        the MCD [dB].    -   Prh=The transmit power of the radio head [dBw].    -   G_amp=The gain of the uplink amplifier of the radio head [dB].    -   L_cable=The determined cable loss [dB].    -   NF_ru=The noise factor of the RU [dB].    -   SINR_mcd_du=The signal to noise and interference ratio of the        MCD, as measured in the DU [dB]    -   P_ul_mcd_du=The MCD power, as measured in the DU [dBw].    -   P_mcd_total=the total power of the MCD    -   N0=Thermal noise power [dBw].    -   I_du=Inter-cell interference [dBw].    -   C_length=a cable length value    -   AECID=Adaptive enhanced cell ID

The invention claimed is:
 1. A method performed by a positioning systemfor determining the location of a mobile communication device (MCD), themethod comprising: determining a cell in which the MCD is located, thedetermined cell being served by a serving base station connected to aset of radio heads, wherein each one of the radio heads included in theset of radio heads is connected to the base station via a cable, and oneof the radio heads included in the set is serving the MCD; determining acable length value representative of the length of the cable connectingthe base station to the radio head serving the MCD; and obtaining one ormore measured radio property values; forming a fingerprint using boththe determined cable length value and the obtained measured radioproperty values; and using the formed fingerprint to obtain locationinformation for the MCD, wherein the obtained location information isassociated with the formed fingerprint and comprises at least: i) a setof polygon coordinate vectors or ii) a set of coordinates derived fromthe set of polygon coordinate vectors.
 2. The method of claim 1, whereinthe location information comprises the set of polygon coordinatevectors, and the set of polygon coordinate vectors define a polygon andcomprise at least three polygon coordinate vectors, each polygoncoordinate vector comprising at least a first coordinate and a secondcoordinate.
 3. The method of claim 1, wherein the one or more measuredradio property values comprises one or more of: a pathloss value, a cellidentifier, a received signal strength, RSS, value, a timing advance,TA, value, and angle of arrival, AoA, values.
 4. The method of claim 1,wherein using the fingerprint to obtain the location informationcomprises sending the fingerprint to a database server to initiate aquery for location information, wherein the database server isconfigured to use the fingerprint to lookup the location information ina database accessible to the database server.
 5. The method of claim 1,wherein the location information comprises the set of coordinatesderived from the set of polygon coordinate vectors, and the set ofcoordinates derived from the set of polygon coordinate vectorscorresponds to the center of gravity of a polygon defined by the set ofpolygon coordinate vectors.
 6. The method of claim 1, wherein the cablelength value is a cable loss value.
 7. A positioning system fordetermining the location of a mobile communication device (MCD), thepositioning system being adapted to: determine a cell in which the MCDis located, the determined cell being served by a serving base stationconnected to a set of radio heads, wherein each one of the radio headsincluded in the set of radio heads is connected to the base station viaa cable, and one of the radio heads included in the set is serving theMCD; determine a cable length value representative of the length of thecable connecting the base station to the radio head serving the MCD;obtain one or more measured radio property values; form a fingerprintusing both the determined cable length value and the obtained measuredradio property values; and use the formed fingerprint to obtain locationinformation for the WCD, wherein the obtained location information isassociated with the formed fingerprint and comprises at least: i) a setof polygon coordinate vectors or ii) a set of coordinates derived fromthe set of polygon coordinate vectors.
 8. The positioning system ofclaim 7, wherein the location information comprises the set of polygoncoordinate vectors, and the set of polygon coordinate vectors define apolygon and comprise at least three polygon coordinate vectors, eachpolygon coordinate vector comprising at least a first coordinate and asecond coordinate.
 9. The positioning system of claim 7, wherein the oneor more measured radio property values comprises one or more of: apathloss value, a cell identifier, a received signal strength, RSS,value, a timing advance, TA, value, and angle of arrival, AoA, values.10. The positioning system of claim 7, wherein the positioning system isadapted to use the fingerprint to obtain the location information bysending the fingerprint to a database server to initiate a query forlocation information, wherein the database server is configured to usethe fingerprint to lookup the location information in a databaseaccessible to the database server.
 11. The positioning system of claim7, wherein the location information comprises the set of coordinatesderived from the set of polygon coordinate vectors, and the set ofcoordinates derived from the set of polygon coordinate vectorscorresponds to the center of gravity of a polygon defined by the set ofpolygon coordinate vectors.
 12. A method for constructing a database forstoring location information for use in determining the location of auser, the method comprising: determining the location of a mobilecommunication device (MCD), said location being defined by a set of twoor more coordinates; generating a first fingerprint using a cable lengthvalue representing the length of a cable connecting a radio head to abase station, wherein at the time the location of the MCD was determinedthe radio head was serving the MCD; associating the first fingerprintwith the determined location; determining a set of locations whereineach location in the set is associated with a fingerprint matching thefirst fingerprint; forming a polygon based on the determined set oflocations, the polygon being defined by a set of three or more polygoncoordinate vectors, each said polygon coordinate vector identifying adifferent vertex of the polygon; and associating the first fingerprintwith at least the set of polygon coordinate vectors or a set ofcoordinates derived from the set of polygon coordinate vectors.
 13. Themethod of claim 12, further comprising obtaining a measured radioproperty value, wherein generating the fingerprint using the determinedcable length value comprises generating the fingerprint using both thedetermined cable length value and the measured radio property value. 14.The method of claim 13, wherein the measured radio property value is avalue representing a radio signal pathloss.
 15. The method of claim 12,wherein each said polygon coordinate vector consists of a firstcoordinate and a second coordinate.
 16. The method of claim 12, whereineach said polygon coordinate vector consists of a first coordinate, asecond coordinate, and a third coordinate.
 17. A positioning system forconstructing a database for storing location information for use indetermining the location of a user, the positioning system being adaptedto: determine the location of a mobile communication device (MCD), saidlocation being defined by a set of two or more coordinates; generate afirst fingerprint using a cable length value representing the length ofa cable connecting a radio head to a base station, wherein at the timethe location of the MCD was determined the radio head was serving theMCD; associate the first fingerprint with the determined location;determine a set of locations wherein each location in the set isassociated with a fingerprint matching the first fingerprint; form apolygon based on the determined set of locations, the polygon beingdefined by a set of three or more polygon coordinate vectors, each saidpolygon coordinate vector identifying a different vertex of the polygon;and associate the first fingerprint with at least the set of polygoncoordinate vectors or a set of coordinates derived from the set ofpolygon coordinate vectors.
 18. The positioning system of claim 17,wherein the positioning system is further adapted to obtain a measuredradio property value and generate the fingerprint using both thedetermined cable length value and the measured radio property value. 19.The positioning system of claim 18, wherein the measured radio propertyvalue is a value representing a radio signal pathloss.
 20. Thepositioning system of claim 17, wherein each said polygon coordinatevector consists of a first coordinate and a second coordinate.
 21. Thepositioning system of claim 17, wherein each said polygon coordinatevector consists of a first coordinate, a second coordinate, and a thirdcoordinate.